Teleological reasoning would conclude the existence of a destined function of the mastoid air cells. The function is alleged to be well established in man. The demonstration of its existence is attempted in different ways.
Hypothetically, functions of varying nature may be ascribed to the mastoid air-cell system. A weight-reducing effect in birds is obvious. An insulating effect against differing climatic conditions may plausibly be considered. This may be of importance for all elements of the inner ear or for only one of them. Furthermore, the addition of the air cube to the middle-ear spaces may serve for an adjustment of air-pressure variations caused by the exchange of air through the open or partially closed tubal canal and by resorption. This may be of importance for the movement of the drum membrane and the hearing.
Judging from the otological literature, a sound-silencing effect has been ascribed to the mastoid air